1. Field of the Invention
The present invention relates to a refrigerant compressor applied to, for example, an air conditioner.
2. Description of the Prior Art
An example of an compressor is shown in FIG. 1. The compressor shown in FIG. 1 is the one for air conditioner for car. FIG. 1 (a) is a sectional view of the compressor. FIG. 1 (b) is a sectional view of compressing-mechanism system. The compressing-mechanism system is constituted mainly of a cylinder 14 (made of iron), a side plate 13 (made of aluminum) for sealing the cylinder 14, an O-ring 15 for improving the sealing between the cylinder 14 and the side plate 13, a rotor rotating in the cylinder 14 to compress refrigerant, and a vane 11 (made of aluminum). The rotor 12 rotates as a rotating shaft 20 supported on a needle bearing 19 rotates.
Such a compressor as having the above compressing-mechanism is assembled after an oil for application is applied in advance to the vane 11, the O-ring 15 and a lip seal 16 etc. After the assembly of the compressor is finished, about 5 cc of an oil for assembly is poured through an intake inlet 17 and enclosed. This oil for assembly is supposed to flow around sliding portions in the compressor, such as a sliding portion between the vane 11 and the side plate 13, a sliding portion between the vane 11 and the cylinder 14, a sliding portion between the rotor 12 and the side plate 13, a sliding portion between the rotor 12 and the cylinder 14, and a sliding portion between the rotating shaft 20 and the needle bearing 19. These sliding portions are indicated by the reference number 3 in FIG. 1. A lubricating oil 2 is poured through an outlet 18 and enclosed in the compressor 1.
In such a compressor, an oil for applying to parts of the compressor and that for assembly have the same basic ingredients as a lubricating oil to be charged in the compressor. A compatible oil having compatibility with a refrigerant has been used for both this lubricating oil and the oil for application or assembly.
Some techniques use non-compatible oils for the lubricating oil and the oil for application or assembly, which do not have compatibility with a refrigerant, as disclosed in, for example, Japanese Patent Laid-Open Hei 5-157379.
However, the constitution using the above-mentioned compatible oil raises the following problem, for example. The compressor is installed in a car to form such a refrigerant circuit as shown in FIG. 2. When the car is left under a burning sun in summer, the temperature of evaporator 5 in the car room goes up higher than that of the compressor 1 and a condenser 4 outside the car room in the daytime. The refrigerant is condensed in the compressor 1 and the condenser 4. The refrigerant dissolves in the lubricating oil particularly well. Then, the sun sets and the temperature difference between the inside and outside of the car disappears. The lubricating oil dissolved in the refrigerant moves from the compressor 1 to the evaporator 5 etc. together with the refrigerant. When this phenomenon is repeated, the lubricating oil goes out of the compressor 1 to move and be held in the condenser 4 and the evaporator 5 etc. in the refrigerant circuit shown in FIG. 2. Thus, there arises a problem that a failure in lubricity occurred when starting the compressor 1 because of a shortage of the lubricating oil.
Further, under the constitution using a non-compatible oil, the oil discharged into the refrigerant circuit from the compressor 1 remains in the refrigerant circuit without returning to the compressor 1 together with the refrigerant even when the refrigerant was circulated, because the oil does not have compatibility with the refrigerant. Therefore, there arises a problem that a shortage of the lubricating oil in the compressor 1 and abnormal wear particularly at the sliding portions 3 occurred to degrade durability of the compressor 1.
In the refrigerant circuit using an open system compressor 1, such an air conditioner for car, two-phase separation between oil and refrigerant occurs when the refrigerant is in short and milkiness is observed at the side glass part 7 of the dryer receiver 6 as shown in FIGS. 3(a) and (b). At this time, when the shortage of the refrigerant is supplemented and the required amount of refrigerant is supplied in the refrigerant circuit, the milkiness disappears. Accordingly, the milkiness phenomenon is one of standards on whether the refrigerant should be supplemented.
However, when using a non-compatible oil or a mixture of a compatible oil and a non-compatible oil, two-phase separation of the non-compatible oil from the refrigerant occurs in the refrigerant circuit.
Therefore, even if a suitable amount of the refrigerant is charged in the refrigerant circuit, milkiness is always observed due to the two-phase separation at the side glass part 7 of the dryer receiver 6 to cause a mistake about a shortage of the refrigerant. As a result, this mistake may lead to unnecessary supplement of the refrigerant, resulting in a problem of excess supplement of the refrigerant.